Elastomer die plug

ABSTRACT

An elastomer die plug for sealing or plugging a hole in an object, such as a coolant passage in an injection molding die. The plug includes a flexible, hollow cylindrical sleeve and a core member longitudinally interengageable into the sleeve. The core member is slightly larger than the bore of the sleeve and when drawn into the sleeve expands it to fill the hole and secure the plug. The plug may be used either internally as a diverting plug or externally as a sealing plug. The inserting tool is designed to position the plug in the hole as desired, and to interengage the core member into the sleeve. The plug is inserted into the hole with the sleeve and core member separate. Then the sleeve is supported in position and the core is interengaged into the sleeve.

This is a division of application Ser. No. 856,679 filed Apr. 25, 1986,now Pat. No. 4,765,049, which is a division of application Ser. No.549,294 filed Nov. 7, 1983, now U.S. Pat. No. 4,584,755 issued Apr. 29,1986.

BACKGROUND OF THE INVENTION

This invention relates to plugging a hole in an object, and particularlyto a plug, inserting tool and the method for plugging an unused coolantpassage or the like in an injection molding die.

In almost all cases where a product is manufactured by forming it in adie or mold, the die body will incorporate drilled passages for a liquidcooling or heating medium. This is true in injection plastic molding,injection rubber molding and metal die casting. In thermoform and diecasting processes, the die is cooled by a liquid medium, usually water,in the drilled passages. In thermoset processes, the die is heated byhot oil or steam circulated through the drilled passages.

With only the exception of a drilled passage with an inlet and outlet onits two openings, all interconnecting drilled passages must have someprovision for plugging unused openings to prevent external leaking.Further, when a labyrinth pattern is formed in the die body byintersecting a passage with three or more perpendicular passages, someform of diverting plug is used to cause the liquid to flow in theprescribed flow path.

General prior practice among tool and die makers is to seal an unusedexternal opening with a threaded pipe plug. This is a secure andeffective solution, although it requires machine time to form thethreads.

An alternative to the pipe plug is a threadless pressure plug, which hasa screw that squeezes and expands an O-ring. This approach has theadvantage of eliminating the time necessary to machine threads. However,the expansion plug is considerably more expensive than a pipe plug.

In those cases where internal passages are plugged to divert the liquidflow, there are a number of prior products or techniques used in thetool and die trade to seal the unused passages. The threadless expansionplug is often used, although it is complicated to position and tighten.In a blind hole, that is, where there is access only from one end, thedie maker must be careful not to press it further into the hole beyondthe position where it is desired.

More commonly used are plug-and-spacer arrangements wherein a slip-fitplug blocks the drilled passage and is positioned by small diameterrods. In some applications, the tool and die shop may manufacture itsown spool shaft by reducing the diameter of a slip-fit rod in thoseareas where flow is desired. Each of the present designs has inherentlimitations. In the case of plug-and-spacer arrangements, the sealaround the plug is never complete. Because the drilled passage is rough,clearance is required to push the plug to the required depth. Theresulting leakage past the plug area may be sufficient to alter theliquid flow, especially when the flow is restricted at the manifoldvalves to control die temperature. Further, the small diameter rods usedin the flow area can accrete liquid-borne contaminants causing aneventual accumulation which can restrict or plug the entire passagesystem. The time required to manufacture and fit a plug-and-spacerdiverting system is also a factor to be considered, especially whenmachining is required.

Accordingly, it is the general object of the present invention toprovide a plug for sealing a hole in an object, particularly a coolantpassage in an injection molding die, a tool for inserting the plug, anda method of so doing.

A further object is to provide such a plug which is easily andaccurately positionable in a blind hole.

Another object is to provide a plug which is very simple to manufactureat low cost.

A further object is to provide an inserting tool for the plug which isable to be operated from only one end of a hole.

Still another object is to provide such a tool which accurately placesthe plug at the desired location in the hole.

A still further object is to provide a method or system of installingthe plugs of the present invention.

These and other objects and advantages of the present invention and themanner in which they are achieved will be made apparent as thespecification and claims proceed, taken in conjunction with the drawingswhich illustrate the preferred embodiment.

SUMMARY OF THE INVENTION

In its basic form, the invention is a plug for sealing a hole in anobject such as an injection molding die, a tool for installing the plug,and a method of so doing. The plug includes a flexible sleeve, generallyof a hollow cylindrical configuration, having a longitudinal boretherethrough leaving a substantially uniform sleeve wall, and having anoutside radial dimension slightly smaller than the hole when the plug isin its unassembled condition, and being expansable to an outside radialdimension which fills the hole when the plug is assembled, and animpervious core member, generally of a cylindrical configuration, anddimensioned slightly larger in radial dimension than the bore of theunassembled sleeve, the core member being operable to longitudinallyinterengage and radially expand the sleeve into sealing engagement withthe hole wall upon assembly. The inserting tool is designed to positionand interengage the plug at a location in the hole as desired.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a fragmentary side view of the inserting tool, with anunassembled plug mounted thereon ready for insertion according to thepresent invention.

FIG. 2 is a fragmentary view of the end of the inserting tool and theplug, similar to FIG. 1, additionally illustrating the use of a sleeveadapter.

FIG. 3 is a fragmentary view similar to FIG. 2, illustrating a secondembodiment of the sleeve adapter.

FIG. 4 is a fragmentary section taken along the line 4--4 of FIG. 1.

FIG. 5 is a section of the assembled plug, shown fully assembled in afragmentary portion of an object.

FIG. 6 is a schematic section showing the plan for installing the plugof the present invention in a labyrinth pattern of drilled passages inan injection molding die.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 6 illustrates a mold base, shown generally at 10, in which asection is taken on a labyrinth pattern of cooling passages. Holes 12and 14 are drilled vertically into the mold base. Interconnectinghorizontal holes 16, 18, 20 and 22 are drilled to intersect verticalholes 12 and 14. None of the holes need to be drilled completely throughthe mold base.

The pattern for plugging the interconnecting passages is illustratedschematically in FIG. 6. Both internal plugs 24, 26 and 28 and externalplugs 30, 32, 34 and 36 are required. The appropriate plugs in thepositions shown direct the collant through the passages in the mold baseas shown by the arrows.

Appropriate connections are made to the inlet 38 and the outlet 40 forsupplying coolant to the mold base.

While the above description is directed to a plastic injection die, itmust be realized that a similar configuration is also applicable inmetal die casting which also uses coolant, and thermoset injectionmolding in which a heating medium is passed through the passages. Itshould also be understood that while the present invention hasparticular utility to plugging passages in a molding die, it may also beused to plug a hole, under similar circumstances, in any other object.

The plug of the present invention is illustrated in FIG. 1 generally at42, and in FIGS. 2, 3 and 5, shown in larger version, generally at 42'.

The plug has two parts, the first of which is a flexible sleeve 44. Thesleeve is preferably of an elastomeric material. It is preferably coatedwith a suitable rubber lubricant (not shown) to facilitate assembly ofthe plug. The sleeve is of a hollow cylindrical configuration, having alongitudinal bore 46 therethrough. This leaves a substantially uniformsleeve wall 48.

When the plug is in its unassembled condition, the outside radialdimension is slightly smaller than the hole which it is to plug.However, it is expansible to an outside radial dimension which fills thehole when the plug is assembled. The leading end of the sleeve, the endfirst inserted into the hole, is tapered on the outside surface thereofat 50 to facilitate the insertion of the sleeve into the hole.

The other part of the plug is a core member, shown generally at 52. Thecore is impervious and is preferably made of brass of similar material.It is generally of a cylindrical configuration, and is dimensionedslightly larger in radial dimension than the bore 46 of the unassembledsleeve 44. The core member is operable to longitudinally interengage thesleeve by being pulled into the bore. This radially expands the sleeveinto sealing engagement with the wall of the hole into which it isinserted. The core member includes engagement means for releasablyattaching a pulling means thereto to draw the core into the sleeve. Forthis purpose, the core preferably includes a threaded blind hole 54 inits end which is engageable with a threaded pulling rod. The leading endof the core member, the end first engaging the sleeve, is tapered on theoutside surface thereof at 56 to facilitate interengagement with thesleeve. The trailing edges of the core member are also preferablytapered or beveled at 58.

A plug similar to that shown at 42 in FIG. 1, but larger in radialdimension, is illustrated in FIGS. 2, 3 and 5. The plug is showngenerally at 42' and analogous features to those of the plug of FIG. 1are also denoted by primed reference numerals.

FIG. 5 shows the plug 42' in assembled condition in a hole in an objectsuch as hole 12 in mold base 10. Core member 52' has been drawn intosleeve 44'. This radially expanded the sleeve and caused it to bepressed into intimate contact with the hole wall. The elastomer sleeveconstricts over the ends of the core member since the core member isshorter than the sleeve and is beveled on both ends, at 56' and 58'.This arrangement, with the core member longitudinally positioned withinthe sleeve, securely anchors the plug from pressure-induced movement.However, the bevel aids plug removal in those rare causes when it isnecessary to drive or drill out the plug.

Now referring to FIGS. 1 and 4, a tool is disclosed for inserting thepreviously described plug into a hole in an object and seating the plugat a particular location in the hole. The tool is shown generally at 60,and includes an elongated, substantially straight tube 62. The tube isof a diameter smaller than the hole, and may be as long as desired, asnoted by the fragmentary break in FIG. 1. At the forward end of thetube, an abutment surface 64 is provided for supporting the rear end ofsleeve 44.

A rod 60 extends longitudinally through the tube. Its forward andrearward ends are threaded, and for convenience of manufacture, may bethreaded its entire length. The forward threaded end is denoted at 68and engages the threaded hole 54 in core 52. The threaded rearward endof the rod is denoted at 70.

A squeeze handle is mounted on tube 62 and includes a stationary fronthandle 72 secured to the tube. A movable rear handle 74 is pivoted tothe front handle at pivot 76. A spring 78 biases the handles outwardly.As best shown in FIG. 4, a rivet and spacer 80 provides rigidity for thesplit top portion of handle 74. The movable handle includes a rearwardlyfacing cam surface 82 which, when it is rotated about pivot 76 uponsqueezing the handle, presents a smooth rearward motion along thelongitudinal direction of tube 62.

An adjusting cylinder 84 is screwed onto the threaded rear end 70 of rod66. The adjusting cylinder includes a guide surface 86 which overlapsthe rear end of tube 62. It may be rotated to allow more or less of therod to extend through the tube. The forward end of the adjustingcylinder includes a cam bearing surface 88 which abuts the cam surface82 of handle 74.

A lock nut 90 is screwed onto the threaded rearward end 70 of rod 66 andabuts the adjusting cylinder to lock the assembly on the threaded rod.The outside surface of the lock nut may be knurled as may the outsidesurface of the adjusting cylinder.

Preferably, tube 62 includes markings or measuring indicia, illustratedat 92, for determining the extension of the tube into the hole. Thesemay be standard inch markings or may be any other measurement system asdesired.

FIG. 2 illustrates a sleeve adapter, shown generally at 94, which isreleasably mounted on the end of tube 62. The sleeve adapter has alarger abutment surface 96 on its forward end than that of the tube. Thelarger abut ent surface provides a more stable base for supporting therear end of larger sleeve 44'.

A second embodiment of the sleeve adapter is illustrated in FIG. 3,generally at 100. In this embodiment, the sleeve adapter is threaded tofit on the threaded end 102 of tube 62'. Again, the larger abutmentsurface 104 is provided for supporting the rear end of sleeve 44'.

OPERATION

The present invention provides a plug which may be used eitherinternally in a hole in an object, or externally at the opening of thehole. It also provides a tool for installing the plug at the desiredlocation in a hole.

In order to ready the assembly for installing a plug in a hole, the toolis initially adjusted by manipulating adjusting cylinder 84 and lock nut90 on the threaded rearward end 70 of rod 66 so that the appropriateamount of the threaded forward end 68 of the rod extends from the end oftube 62.

According to the size of the hole, an appropriate sleeve adapter 94 or100 is selected and is placed on the end of tube 62.

Sleeve 44 is then placed over the forward end of rod 66, and the rearend of the sleeve abuts the abutment surface 64 of tube 62. Core member52 is then screwed onto the threaded forward end 68 of rod 66 and inthis position assumes the configuration of FIG. 1.

The depth for the plug is measured, which is often done by using thetool itself, and the appropriate depth for insertion is noted on indicia92.

The core member 52 and flexible sleeve 44 are then inserted into thehole up to the proper location according to indicia 92. The forwardtapered end 50 of the sleeve aids the insertion into the hole.

As yet, the core member and flexible sleeve are separate, not havingbeen interengaged.

The tapered leading end 56 of core member 52 is directed rearwardly,abutting the forward end of sleeve 44. Upon squeezing handles 72 and 74,cam surface 82 presses rearwardly on the cam bearing member 88 ofadjusting cylinder 84. This draws rod 66 rearwardly in relation to tube62. The tapered end of the core member enters the sleeve and the core isinterengaged into the sleeve.

Because the outside dimension of core 52 is slightly larger than thebore 46 of plug 44, the interengagement radially expands the sleeve intosealing engagement with the hole wall. According to the adjustment ofthe adjusting cylinder 84, the draw of the core member into the sleeveis stopped while the core is positioned entirely inside of the sleeve.Even if the draw is longer than optimum, the front edge of the coreabuts the forward surface 64 of tube 62 and will not pull further.

The squeezed handles 72 and 74 are then released and the solidifiedassembly of the adjusting cylinder 84, lock nut 90 and rod 66 is rotatedto unscrew the threaded forward end 68 of the rod from the threaded hole54 in the core member.

The tool is then withdrawn, leaving the assembled plug in the hole,similar to the plug shown in FIG. 5.

While the foregoing is the preferred method of using the apparatus ofthe present invention, it may be appreciated that various methods ofassembly could be employed. However, it is contemplated that in mostapplications, the holes drilled into an injection molding die areaccessable from only one end, and accordingly the method of assemblymust work reliably from just one opening. In this regard, the coremember is preferably inserted into the hole ahead of the sleeve and thendrawn into the sleeve while the rear end of the sleeve is supported atthe proper location in the hole. Obviously, however, various pullingmeans or pressing means may engage the plug directly or via someengagement means to effect the interengagement of the plug.

It can be seen that a very useful, simple and reliable apparatus andmethod for plugging a hole in an object is provided by the presentinvention. Only the preferred apparatus and method have been elaboratedupon, and no limitation is intended thereby. Obvious modifications maybe made by those skilled in the art without departing from the spiritand scope of the invention.

Having described my invention in its preferred embodiment, I claim:
 1. Aplug for sealing a substantially cylindrical hole in an object,comprising:(a) a flexible elastomer sleeve, generally of a hollowcylindrical configuration, having a longitudinal bore therethroughleaving a substantially uniform sleeve wall, and having an outsideradial dimension slightly smaller than the hole when the plug is in itsunassembled condition, and being expansible to an outside radialdimension which fills the hole when the plug is assembled; and (b) animpervious core member, generally of a cylindrical configuration, anddimensioned slightly larger in radial dimension than the bore of theunassembled sleeve, the core member being operable to longitudinallyinterengage and radially expand the sleeve into sealing engagement withthe hole wall upon assembly said core member having a length shorterthan said sleeve and a leading end of the core member for first engagingthe sleeve being tapered on the outside surface thereof to facilitateassembly thereof longitudinally within the sleeve when the plug isassembled, and said core member further including an internal engagementmeans for releasably attaching a pulling means to the core member todraw the core member into the sleeve.
 2. The plug of claim 1 wherein theleading end of the sleeve, first inserted into the hole, is tapered onthe outside surface thereof to facilitate insertion into the hole. 3.The plug of claim 1 wherein the outside surface of the leading andtrailing edges of the core member are tapered and wherein the ends ofthe sleeve constrict over the ends of the core member.
 4. The plug ofclaim 1 wherein the engagement means comprises the threads in a blindhole in the core member for engagement with a threaded pulling means.